Ron Bridges

I'm having sound problems with my SoundMax Integrated Digital HD Audio (Asus P5N-T Deluxe Motherboard) and Klipsch ProMedia 4.1 When I plug the rear speaker jack in to the rear port and front speakers into the front port and test with the sound max software on quadraphonic I get the correct tones from each speaker, but when I play mp3's only the front speakers play. The only way I can get all the speakers to play is to plug front and rear into a splitter and then to the front speaker port which is ok, but does not sound that good when I play games. Any Ideas? My OS is windows 7 Ultimate and windows media player I just noticed that there is a setting in windows media player that has an optin to play from default device or SoundMax Integrated Digital HD Audio, but media player will not let me switch to that option.